Re: [PATCH 0/3] Add VGA support for Apalis iMX6

[Francesco Dolcini <francesco@dolcini.it>]

Hello Laurent,

On Mon, Oct 12, 2026 at 06:40:54PM +0200, Laurent Pinchart wrote:
> On Mon, Oct 12, 2026 at 04:25:22AM -0300, Leonardo Costa wrote:
> > This series adds a device tree overlay that enables the VGA output on Apalis
> > iMX6, which is driven from a parallel RGB interface passing through a
> > non-programmable video DAC.
> > 
> > The video DAC is a simple resistor network gated by an active-low
> > data-enable signal. For the bridge to work properly, this series also
> > changes the following in the dt-bindings and simple-bridge driver:
> > 
> > - dt-bindings: Add a new compatible for the bridge in the simple-bridge
> >   binding. This is necessary because the existing dumb-vga-dac compatible
> >   doesn't describe a data-enable signal polarity.
> > 
> > - simple-bridge: Add the VGA bridge match-table entry and timings
> >   struct, setting the DRM_BUS_FLAG_DE_LOW flag for the bridge.
> 
> Is there schematics available anywhere ? That would help reviewing the
> series ?

This circuit is on the SoM, and the SoM schematics are
confidential and not generally available.

I tried to extract as ascii art the relevant circuit, hope it helps

BLUE (5 bits)
=============
DISP0_DATA[4] ---[R30   348R]---+
DISP0_DATA[3] ---[R33   715R]---+
DISP0_DATA[2] ---[R36  1.47K]---+-------- VGA1_B
DISP0_DATA[1] ---[R39  2.94K]---+          |
DISP0_DATA[0] ---[R42  5.90K]---+          D
                                           |
DI0_PIN15 ------------------------------ G | T4 MMBF2201N
                                           S
                                           |
                                          GND


RED (5 bits)
============
DISP0_DATA[15] --[R31   348R]---+
DISP0_DATA[14] --[R34   715R]---+
DISP0_DATA[13] --[R37  1.47K]---+-------- VGA1_R
DISP0_DATA[12] --[R40  2.94K]---+          |
DISP0_DATA[11] --[R43  5.90K]---+          D
                                           |
DI0_PIN15 ------------------------------ G | T5 MMBF2201N
                                           S
                                           |
                                          GND


GREEN (6 bits)
==============
DISP0_DATA[10] --[R32   348R]---+
DISP0_DATA[9]  --[R35   715R]---+
DISP0_DATA[8]  --[R38  1.47K]---+
DISP0_DATA[7]  --[R41  2.94K]---+-------- VGA1_G
DISP0_DATA[6]  --[R44  5.90K]---+          |
DISP0_DATA[5]  --[R45  11.8K]---+          D
                                           |
DI0_PIN15 ------------------------------ G | T6 MMBF2201N
                                           S
                                           |
                                          GND



Francesco